U.S. patent application number 13/255815 was filed with the patent office on 2012-01-05 for hydraulic driving device for work machine.
This patent application is currently assigned to Hitachi Construction Machinery Co., Ltd.. Invention is credited to Hiroyuki Azuma, Naoki Hagiwara, Kouji Ishikawa, Mitsuhiko Kanehama, Tsuyoshi Nakamura, Yasuo Okano, Kensuke Sato.
Application Number | 20120000191 13/255815 |
Document ID | / |
Family ID | 42728364 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120000191 |
Kind Code |
A1 |
Hagiwara; Naoki ; et
al. |
January 5, 2012 |
Hydraulic Driving Device for Work Machine
Abstract
Disclosed is a hydraulic drive system for a working machine,
which enables to conduct forced regeneration continuously for a
sufficient time. Based on an input of a lock detection signal S1
from a gate lock detection switch 40, a controller 50 detects that
a gate lock lever 32 for controlling a gate lock on/off valve 33 is
in a locked state, in other words, hydraulic actuators such as an
arm cylinder 12 arranged on a hydraulic excavator 1 are all in
non-operated states. Upon an input of a forced regeneration command
signal So from a forced regeneration switch 53 in this detected
state, control signals Cp,Cf are outputted to a boosting control
valve 51 and regulator 52 to make a forced regeneration means (an
arm cylinder control valve 27 and the regulator 52) conduct forced
regeneration.
Inventors: |
Hagiwara; Naoki;
(Tsuchiura-shi, JP) ; Nakamura; Tsuyoshi;
(Tsuchiura-shi, JP) ; Sato; Kensuke;
(Tsuchiura-shi, JP) ; Okano; Yasuo;
(Tsuchiura-shi, JP) ; Ishikawa; Kouji;
(Tsuchiura-shi, JP) ; Kanehama; Mitsuhiko;
(Tsuchiura-shi, JP) ; Azuma; Hiroyuki;
(Tsuchiura-shi, JP) |
Assignee: |
Hitachi Construction Machinery Co.,
Ltd.
Bunkyo-ku, Tokyo
JP
|
Family ID: |
42728364 |
Appl. No.: |
13/255815 |
Filed: |
March 9, 2010 |
PCT Filed: |
March 9, 2010 |
PCT NO: |
PCT/JP2010/053892 |
371 Date: |
September 9, 2011 |
Current U.S.
Class: |
60/311 |
Current CPC
Class: |
F15B 2211/6653 20130101;
F01N 3/023 20130101; F15B 2211/6346 20130101; F15B 2211/85
20130101; F15B 2211/20546 20130101; F15B 2211/665 20130101; E02F
9/2246 20130101; F15B 2211/6652 20130101; E02F 9/2296 20130101;
F15B 2211/67 20130101; F15B 2211/634 20130101; F02D 41/029
20130101; F15B 2211/20523 20130101; E02F 9/0866 20130101; E02F
9/2285 20130101; E02F 9/2217 20130101; F15B 2211/25 20130101; E02F
9/2235 20130101; F15B 21/082 20130101; B01D 46/0063 20130101; B01D
46/42 20130101; F02D 2041/026 20130101; F15B 2211/6355 20130101;
F15B 2211/6658 20130101; E02F 9/2066 20130101 |
Class at
Publication: |
60/311 |
International
Class: |
F01N 3/023 20060101
F01N003/023; F15B 13/00 20060101 F15B013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2009 |
JP |
2009058474 |
Claims
1. A hydraulic drive system for a working machine, said hydraulic
drive system being provided with plural hydraulic actuators for
driving the working machine, a hydraulic pressure source for
producing, by a hydraulic pump, pressure oil to be fed to the
plural hydraulic actuators, control valves separately arranged for
the plural hydraulic actuators, respectively, to control flows of
pressure oil between the corresponding hydraulic actuators and the
hydraulic pressure source, an engine as a drive source for the
hydraulic pump, an exhaust gas purification device for capturing,
by a filter, particulate matter in exhaust gas produced by the
engine, a forced regeneration means for burning particulate matter
deposited on the filter, and a control means for controlling the
forced regeneration means, said forced regeneration means serving
to raise a delivery pressure of the hydraulic pump to increase an
engine output such that the exhaust gas is provided with heat
needed to burn the particulate matter, wherein: valve positions of
the control valves are set to change between initial positions, in
which the flows of pressure oil from the hydraulic pressure source
to the hydraulic actuators are cut off to guide the pressure oil to
a hydraulic oil reservoir, and operating positions, in which the
pressure oil from the hydraulic pressure source is guided to the
corresponding hydraulic actuators; the forced regeneration means
includes a specific one of the control valves as a means for
raising the delivery pressure of the hydraulic pump; the hydraulic
drive system is further provided with a forced regeneration command
means for commanding conduct of forced regeneration when operated,
and also with a non-operated state detecting means for detecting a
non-operated state in which the valve positions of all the control
valves are in states of the initial positions; and taking as a
condition for the conduct of forced regeneration that a
non-operated state has been detected by the non-operated state
detecting means, the control means actuates the specific control
valve to raise the delivery pressure of the hydraulic pump when the
conduct of forced regeneration is commanded by the forced
regeneration command means.
2. The hydraulic drive system according to the invention as
described in claim 1, wherein: working equipment of the working
machine is provided with a boom and an arm pivotally connected to
the boom; the plural hydraulic actuators include an arm cylinder;
the specific control valve is an arm cylinder control valve for
controlling a flow of pressure oil between the arm cylinder and the
hydraulic pressure source; the hydraulic drive system is further
provided with a stroke-end state detection means for detecting that
the arm cylinder has been brought into a state of a stroke end on a
side where a free end of the arm is brought close to the boom; and
the control means controls the arm cylinder control valve such that
the arm cylinder operates toward the stroke end, and based on
detection results by the stroke-end state detection means, also
controls the arm cylinder control valve such that the stroke-end
state of the arm cylinder is maintained during the forced
regeneration.
3. The hydraulic drive system according to the invention as
described in claim 1, wherein: working equipment of the working
machine is provided with a boom, an arm pivotally connected to the
boom, and a bucket or attachment pivotally connected to the arm;
the plural hydraulic actuators include a bucket cylinder for
pivoting the bucket or attachment connected to the arm; the
specific control valve is a bucket cylinder control valve for
controlling a flow of pressure oil between the bucket cylinder and
the hydraulic pressure source; the hydraulic drive system is
further provided with a stroke-end state detection means for
detecting that the bucket cylinder has been brought into a state of
a stroke end on an extended side or contracted side thereof; and
the control means controls the bucket cylinder control valve such
that the bucket cylinder operates toward the stroke end, and based
on detection results by the stroke-end state detection means, also
controls the bucket cylinder control valve such that the stroke-end
state of the bucket cylinder is maintained during the forced
regeneration.
4. The hydraulic drive system according to the invention as
described in claim 2, wherein: the stroke-end state detection means
detects the state of the stroke end of the arm cylinder based on an
attitude of the arm relative to the boom.
5. The hydraulic drive system according to the invention as
described in claim 3, wherein: the stroke-end state detection means
detects the state of the stroke end of the bucket cylinder based on
an attitude of the bucket or attachment relative to the arm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a hydraulic drive system
for a working machine such as a hydraulic cylinder. The hydraulic
drive system can be adopted in the working machine, is provided
with an exhaust gas purification device for capturing, by a filter,
particulate matter in exhaust gas produced through incomplete
combustion in an engine (prime mover), and burns particulate matter
deposited on the filter to conduct its removal (so-called forced
regeneration).
BACKGROUND ART
[0002] Conventionally, a hydraulic drive system for a working
machine has been designed to permit detecting clogging of a filter
in an exhaust gas purification device. When the working machine is
in a non-operated state at the time of detection of clogging, the
hydraulic drive system automatically performs both raising the
delivery pressure of a hydraulic pump and increasing the delivery
flow rate of the hydraulic pump in parallel, whereby an engine
output is increased. This increase in engine output leads to a rise
in the temperature of exhaust gas. When the temperature of the
exhaust gas rises to a temperature needed for the burning of
particulate matter, the particulate matter with which the filter is
clogged burns off (see Patent Document 1).
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: JP-B-3073380
DISCLOSURE OF THE INVENTION
Problem to Be Solved by the Invention
[0004] The above-mentioned, conventional hydraulic drive system
automatically conducts forced regeneration in a non-operated state
of the working machine, so that the continuation time of the forced
regeneration depends on the length of the lasting time of the
non-operated sate and the forced regeneration may not always be
conducted continuously for a sufficient time. If forced
regeneration of insufficient continuation time is repeated,
particulate matter burns off in every forced regeneration in the
filter at areas where the temperature is easy to rise, but at areas
where the temperature is hard to rise, particulate matter does not
sufficiently burn and remains and the deposit of particulate matter
continues to proceed. Localized clogging of the filter as a result
of such localized deposit of particulate matter as described above
is more difficult to detect than overall clogging of the filter.
Localized clogging of the filter, therefore, tends to be left
uncleaned, thereby causing a reduction in engine output during
operation of the working machine.
[0005] With the foregoing circumstances in view, the present
invention has as an object thereof the provision of a hydraulic
drive system for a working machine, which can conduct forced
regeneration continuously for a sufficient time.
Means for Solving the Problem
[0006] To achieve the above-described object, the present invention
is constituted as will be described next. [0007] [1] The present
invention is characterized in that in a hydraulic drive system for
a working machine, said hydraulic drive system being provided with
plural hydraulic actuators for driving the working machine, a
hydraulic pressure source for producing, by a hydraulic pump,
pressure oil to be fed to the plural hydraulic actuators, control
valves separately arranged for the plural hydraulic actuators,
respectively, to control flows of pressure oil between the
corresponding hydraulic actuators and the hydraulic pressure
source, an engine as a drive source for the hydraulic pump, an
exhaust gas purification device for capturing, by a filter,
particulate matter in exhaust gas produced by the engine, a forced
regeneration means for burning particulate matter deposited on the
filter, and a control means for controlling the forced regeneration
means, said forced regeneration means serving to raise a delivery
pressure of the hydraulic pump to increase an engine output such
that the exhaust gas is provided with heat needed to burn the
particulate matter, valve positions of the control valves are set
to change between initial positions, in which the flows of pressure
oil from the hydraulic pressure source to the hydraulic actuators
are cut off to guide the pressure oil to a hydraulic oil reservoir,
and operating positions, in which the pressure oil from the
hydraulic pressure source is guided to the corresponding hydraulic
actuators; the forced regeneration means includes a specific one of
the control valves as a means for raising the delivery pressure of
the hydraulic pump; the hydraulic drive system is further provided
with a forced regeneration command means for commanding conduct of
forced regeneration when operated, and also with a non-operated
state detecting means for detecting a non-operated state in which
the valve positions of all the control valves are in states of the
initial positions; and taking as a condition for the conduct of
forced regeneration that a non-operated state has been detected by
the non-operated state detecting means, the control means actuates
the specific control valve to raise the delivery pressure of the
hydraulic pump when the conduct of forced regeneration is commanded
by the forced regeneration command means.
[0008] In the present invention as described above in [1], the
control means makes the forced regeneration means actuate the
specific control valve to conduct forced regeneration when a
non-operated state has been detected by the non-operated state
detection means upon operation of the forced regeneration command
means. In other words, an operator of the working machine can make
the forced regeneration means initiate forced regeneration by
operating the forced regeneration command means after the valve
positions of all the control valves are brought into the states of
initial positions, that is, into states that the working machine is
inoperative. As a consequence, the operator can take time either
before initiation of work or after completion of work by the
working machine or periodically to purposefully conduct forced
regeneration continuously for a sufficient time. [0009] [2] The
present invention may also be characterized in that in the
invention as described above in [1], working equipment of the
working machine is provided with a boom and an arm pivotally
connected to the boom; the plural hydraulic actuators include an
arm cylinder; the specific control valve is an arm cylinder control
valve for controlling a flow of pressure oil between the arm
cylinder and the hydraulic pressure source; the hydraulic drive
system is further provided with a stroke-end state detection means
for detecting that the arm cylinder has been brought into a state
of a stroke end on a side where a free end of the arm is brought
close to the boom; and the control means controls the arm cylinder
control valve such that the arm cylinder operates toward the stroke
end, and based on detection results by the stroke-end state
detection means, also controls the arm cylinder control valve such
that the stroke-end state of the arm cylinder is maintained during
the forced regeneration.
[0010] In the present invention as described above in [2], the arm
and boom take an attitude as a whole during the forced regeneration
that they are folded back toward a body of the working machine. As
a consequence, the space occupied by the working machine in
horizontal direction during the forced regeneration can be
maintained small. Further, as the motion of the arm upon forced
regeneration, the arm is actuated such that the free end of the arm
comes closer to the boom. Compared with an actuation that moves the
free end of the arm away from the boom, the potential problem that
the working equipment may come into contact with an object around
the working equipment can be made hardly occur accordingly.
[0011] Taking a hydraulic excavator as an example, a description
will be made about the stroke-end state of the arm cylinder.
Hydraulic excavators may be divided into two types, one being
backhoe shovels and the other loading shovels. In a backhoe shovel,
a stroke end on an extended side of an arm cylinder corresponds to
a state of the arm cylinder that the free end of an arm is brought
closest to a boom. In a loading shovel, on the other hand, a stroke
end on a contracted side of an arm cylinder corresponds to a state
of the arm cylinder that the free end of an arm is brought closest
to a boom. [0012] [3] The present invention may also be
characterized in that in the invention as described above in [1],
working equipment of the working machine is provided with a boom,
an arm pivotally connected to the boom, and a bucket or attachment
pivotally connected to the arm; the plural hydraulic actuators
include a bucket cylinder for pivoting the bucket or attachment
connected to the arm; the specific control valve is a bucket
cylinder control valve for controlling a flow of pressure oil
between the bucket cylinder and the hydraulic pressure source; the
hydraulic drive system is further provided with a stroke-end state
detection means for detecting that the bucket cylinder has been
brought into a state of a stroke end on an extended side or
contracted side thereof; and the control means controls the bucket
cylinder control valve such that the bucket cylinder operates
toward the stroke end, and based on detection results by the
stroke-end state detection means, also controls the bucket cylinder
control valve such that the stroke-end state of the bucket cylinder
is maintained during the forced regeneration.
[0013] In the present invention as described above in [3], a part
of the working equipment, said part being to be actuated upon
forced regeneration, is the bucket or attachment. Compared with the
boom and arm, a change in the attitude of the working machine as a
result of the actuation of such a part is limited smaller. Namely,
in the present invention as described above in [3], the working
equipment is actuated in association with forced regeneration but
the forced regeneration can be conducted in a space smaller than
that required for an actuation of the boom or arm out of the
working equipment. [0014] [4] The present invention may also be
characterized in that in the invention as described above in [2],
the stroke-end state detection means detects the state of the
stroke end of the arm cylinder based on an attitude of the arm
relative to the boom.
[0015] Working machines include those which are each provided, at a
joint where a boom and an arm are pivotally connected with each
other, with an angle sensor for detecting an attitude, in other
words, angle of the arm relative to the boom. The present invention
as described above in [4] can detect the stroke-end state of the
arm cylinder by making use of the angle sensor. [0016] [5] The
present invention may also be characterized in that in the
invention as described above in [3], the stroke-end state detection
means detects the state of the stroke end of the bucket cylinder
based on an attitude of the bucket or attachment relative to the
arm.
[0017] Working machines include those which are each provided, at a
joint where an arm and a bucket are pivotally connected with each
other or at a link mechanism interposed between the arm and the
bucket, with an angle sensor for detecting an attitude of the
bucket relative to the arm, in other words, an angle of the bucket
relative to the arm or an angle of the bucket relative to the link
mechanism. The present invention as described above in [5] can
detect the stroke-end state of the bucket cylinder by making use of
the angle sensor.
Advantageous Effects of the Invention
[0018] According to the present invention, the operator can take
time either before initiation of work or after completion of work
by the working machine or periodically to purposefully conduct
forced regeneration continuously for a sufficient time as mentioned
above. The present invention can, therefore, contribute to the
prevention of a reduction in engine output during operation of the
working machine, which would otherwise be caused by leaving
localized clogging of the filter uncleaned in the exhaust gas
purification device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a left side view of a hydraulic excavator as a
working machine according to a first embodiment of the present
invention.
[0020] FIG. 2-1 is a hydraulic circuit diagram showing in a
simplified form a hydraulic drive system arranged in the hydraulic
excavator illustrated in FIG. 1.
[0021] FIG. 2-2 is a flow chart illustrating a flow of processing
to be performed at a controller depicted in FIG. 2-1.
[0022] FIG. 3-1 is a hydraulic circuit diagram showing in a
simplified form a hydraulic drive system according to a second
embodiment of the present invention.
[0023] FIG. 3-2 is a flow chart illustrating a flow of processing
to be performed at a controller depicted in FIG. 3-1.
MODES FOR CARRYING OUT THE INVENTION
[0024] A description will be made about the first and second
embodiments of the present invention.
[First Embodiment]
[0025] With reference to FIGS. 1, 2-1 and 2-2, a description will
be made about the first embodiment. FIG. 1 is a left side view of a
hydraulic excavator as a working machine according to the first
embodiment of the present invention. FIG. 2-1 is a hydraulic
circuit diagram showing in a simplified form a hydraulic drive
system arranged in the hydraulic excavator illustrated in FIG. 1.
FIG. 2-2 is a flow chart illustrating a flow of processing to be
performed at a controller depicted in FIG. 2-1.
[0026] As illustrated in FIG. 1, the hydraulic excavator 1 is
provided with a travel base 2 which runs by driving crawler tracks
3, a revolving upperstructure 4 swingably connected to the travel
base 2, and working equipment 7 substantially centrally arranged on
a front section of the revolving upperstructure 4.
[0027] On a left front section of the revolving upperstructure 4,
an operator's cab 5 is mounted. Disposed behind the operator's cab
5 is an engine compartment 6, in which a main pump 22, engine 23
and the like of a hydraulic drive system 20 to be mentioned
subsequently herein are accommodated. From a top part of the engine
compartment 6, an outlet pipe 26 extends to guide exhaust gas from
the engine 23 outward of the hydraulic excavator 1.
[0028] The working equipment 7 is provided with a boom 8. The boom
8 of the working equipment 7 is pivotally connected at one end
thereof to the revolving upperstructure 4 via a pin. To the
opposite end of the boom 8, an arm 9 is pivotally connected at one
end thereof via a pin. To the opposite end of the arm 9, a bucket
10 is pivotally connected at one end thereof via a pin. The boom 8
is drivable by a boom cylinder 11. This boom cylinder 11 is
pivotally connected at a bottom-side end of a cylinder tube 11a to
the revolving upperstructure 4 via a pin, and is also pivotally
connected at an end of a rod 11b to an intermediate part of the
boom 8 via a pin. The arm 9 is drivable by an arm cylinder 12. This
arm cylinder 12 is pivotally connected at a bottom-side end of a
cylinder tube 12a to the boom 8 via a pin, and is also pivotally
connected at an end of a rod 12b to the one end of the arm 9 via a
pin. The bucket 10 is arranged such that an extending/retracting
motion of a bucket cylinder 13 is transmitted via a link mechanism
13c to drive the bucket 10. This bucket cylinder 13 is pivotally
connected at a bottom-side end of a cylinder tube 13a to the arm 9
via a pin, and is also pivotally connected at an end of a rod 13b
to the link mechanism 13c via a pin.
[0029] As depicted in FIG. 2-1, the hydraulic drive system 20
according to the first embodiment is provided, as plural hydraulic
actuators making up a drive source for the hydraulic excavator 1,
with a left travel motor (not shown) and a right travel motor (not
shown) as a drive source for the travel base 2, a swing motor (not
shown) as a drive source for the revolving upperstructure 4, the
boom cylinder 11, the arm cylinder 12, and the bucket cylinder 13.
(It is to be noted that FIG. 2-1 depicts only the arm cylinder 12
and the remaining hydraulic actuators are omitted.)
[0030] A hydraulic pressure source for a drive pressure to be fed
to these plural hydraulic actuators is the main pump 22
(variable-displacement hydraulic pump). A drive source for this
main pump 22 is the engine 23 (prime mover: diesel engine). An
exhaust gas pipe 24 extends from the engine 23, and this exhaust
gas pipe 24 is provided with an exhaust gas purification device 25.
The exhaust gas purification device 25 serves to capture, by a
filter, particulate matter in exhaust gas produced by incomplete
combustion of fuel in the engine 23. From the exhaust gas
purification device 25, the above-described outlet pipe 26
extends.
[0031] Between the main pump 22 and the respective hydraulic
actuators, actuator control valves are interposed to control the
directions and flows of pressure oil to be fed to the hydraulic
actuators. FIG. 2-1 depicts, as a representative of these actuator
control valves, only an arm cylinder control valve 27 interposed
between the main pump 22 and the arm cylinder 12. This arm cylinder
control valve 27 is a hydraulically-piloted, spring-centered,
3-position valve. The valve position of the arm cylinder control
valve 27 is set such that it changes between an initial position
27c (neutral position) and a first operating position 27d or also
between the initial position 27c and a second operating position
27e. The initial position 27c (neutral position) is a valve
position, in which a passage that guides pressure oil to a
hydraulic oil reservoir 21 is formed while cutting off a flow of
pressure oil from the main pump 22 to either a bottom chamber 12a1
or a rod chamber 12a2 of the arm cylinder 12. The first operating
position 27d is a valve position on a side that the arm cylinder 12
is caused to extend, in which two passages are formed, one being a
passage that guides pressure oil, which has been delivered from the
main pump 22, to the bottom chamber 12a1 of the arm cylinder 12,
and the other a passage that guides pressure oil, which is
contained in the rod chamber 12a2, to the hydraulic oil reservoir
21. The second operating position 27e is a valve position on a side
that the arm cylinder 12 is caused to contract, in which two
passages are formed, one being a passage that guides pressure oil,
which has been delivered from the main pump 22, to the rod chamber
12a2 of the arm cylinder 12, and the other a passage that guides
pressure oil, which is contained in the bottom chamber 12a1, to the
hydraulic oil reservoir 21. A boom cylinder control valve, bucket
cylinder control valve, left travel motor control valve, right
travel motor control valve and swing motor control valve are also
constructed like the arm cylinder control valve 27.
[0032] A pilot pressure to be applied to the arm cylinder control
valve 27 is produced by an arm control device 29. This arm control
device 29 has a pair of lever-operated pilot valves, and using a
delivery pressure of a pilot pump 28 as a primary pressure, a pilot
pressure is produced by one of these pilot valves. Similar control
devices as the arm control device 29 are arranged for the boom
cylinder control valve, bucket cylinder control valve, left travel
motor control valve, right travel motor control valve and swing
motor control valve, respectively.
[0033] A pilot line 31 extending from the pilot pump 28, that is, a
line that guides pressure oil, which is delivered from the pilot
pump 28 and is distributed to all the control devices such as the
arm control device 29, is provided with a gate lock on/off valve 33
which can collectively cut off the primary pressure to all the
control devices.
[0034] The gate lock on/off valve 33 is a lever-operated, spring
return valve, and is operated by a gate lock lever 32. In this gate
lock on/off valve 33, the initial position corresponds to an open
position 33a, and the operating position corresponds to a closed
position 33b. The closed position 33b is a valve position, in which
the pilot line 31 is closed and the primary pressure to all the
control devices such as the arm control device 29 is collectively
cut off. The gate lock lever 32 can be selectively held by an
unillustrated construction in a locked position corresponding to
the valve position of the gate lock on/off valve 33 or in a
canceled position corresponding to the open position 33a of the
gate lock on/off valve 33.
[0035] Attached to the gate lock lever 32 is a lock detection
switch 40, which detects that the gate lock lever 32 is in a locked
position, in other words, in a locked state, and outputs a lock
detection signal S1 (electrical signal).
[0036] On the pin joint that pivotally connects the boom and the
revolving upperstructure 4 with each other, a boom angle sensor 43
is arranged to output an angle of the boom 8 relative to the
revolving upperstructure 4 by converting it into a boom angle
detection signal Sbm (electrical signal). On the pin joint that
pivotally connects the arm 9 and boom 8 with each other, an arm
angle sensor 41 is arranged to output an angle of the arm 9
relative to the boom 8 by converting it into an arm angle detection
signal Sa (electrical signal). On the pin joint that pivotally
connects the arm 9 and bucket 10 with each other, a bucket angle
sensor 42 is arranged to output an angle of the bucket 10 relative
to the arm 9 by converting it into a bucket angle detection signal
Sbt (electrical signal).
[0037] In a main line 30, a delivery pressure sensor 44 is arranged
on a side upstream of all the actuator control valves such as the
arm cylinder control valve 27 to output a delivery pressure of the
main pump 22 by converting it into a delivery pressure detection
signal Sp (electrical signal).
[0038] The arm cylinder control valve 27 has a pair of hydraulic
pilot ports 27a,27b, and these hydraulic pilot ports 27a,27b are
both connected to the arm control device 29. Further, only the
hydraulic pilot port 27a is connected to a boosting control valve
51 in addition to the arm control device 29. When a pilot pressure
is applied to the hydraulic pilot port 27a, a spool of the arm
cylinder control valve 27 is moved to a side where the arm cylinder
12 brings the free end of the arm 9 closer to the boom 8, in other
words, to the side of the first operating position which is the
valve position on a side where the arm cylinder 12 is caused to
extend. The boosting control valve 51 is interposed between an
upstream side of the gate lock on/off valve 33 in the pilot line 31
and the hydraulic pilot port 27a. This boosting control valve 51 is
a spring-return, proportional solenoid valve, and is actuated upon
application of a control signal Cp (electrical signal). An initial
position 51a is a valve position in which a passage is formed to
bring the hydraulic pilot port 27a into communication with the
hydraulic oil reservoir 21. An operating position 51b is a valve
position in which a passage is formed to bring the hydraulic pilot
port 27a into communication with the pilot pump 28. A pilot
pressure to be applied to the hydraulic pilot port 27a changes
steplessly depending on changes in the valve position of the
boosting control valve 51, and becomes higher as the valve position
comes closer to the operating position 51b.
[0039] The delivery flow rate of the main pump 22 is controlled by
a regulator 52. This regulator 52 is electrically operated, and
upon receipt of a control signal Cf (electrical signal), is
actuated in a direction that the delivery flow rate of the main
pump 22 is increased.
[0040] The engine 23 is controlled to obtain an engine output
corresponding to every variation in the load on the main pump 22.
The engine output, therefore, increases when the delivery flow rate
of the main pump 22 increases and the delivery pressure of the main
pump 22 rises. When the temperature of exhaust gas rises as a
result of an increase in engine output and this temperature reaches
a value needed for the burning of particulate matter, forced
regeneration is conducted to burn off the particulate matter
deposited on the filter of the exhaust gas purification device 25.
The hydraulic drive system 20 is designed to permit conducting this
forced regeneration. Upon forced regeneration, a means for
increasing the delivery flow rate of the main pump 22 is the
regulator 52, and as a means for raising the delivery pressure of
the main pump 22, a specific one of all the actuator control
valves, for example, the arm cylinder control valve 27 is used.
Therefore, the arm cylinder control valve 27 and regulator 52 make
up a forced regeneration means for increasing the engine output to
provide the exhaust gas with heat needed to burn the particulate
matter deposited on the filter of the exhaust gas purification
device 25.
[0041] As a forced regeneration command means for commanding the
conduct of forced regeneration when operated by a part of the body,
a forced regeneration switch 53 is arranged. This forced
regeneration switch 53 is a spring-return, push-button switch, and
in its ON state, outputs a forced regeneration command signal So
(electrical signal) as a command for conducting forced
regeneration.
[0042] The lock detection signal S1 outputted from the lock
detection switch 40, the boom angle detection signal Sbm outputted
from the boom angle sensor 43, the arm angle detection signal Sa
outputted from the arm angle sensor 41, the bucket angle detection
signal Sbt outputted from the bucket angle sensor 42, the delivery
pressure detection signal Sp outputted from the delivery pressure
sensor 44 and the forced regeneration command signal So outputted
from the forced regeneration switch 53 are inputted to the
controller 50.
[0043] The controller 50 is a unit, which is provided with
[0044] CPU, ROM, RAM and the like and is operated in accordance
with a computer program. This controller 50 is set to determine
whether or not the lock detection signal S1 has been applied from
the lock detection switch 40. When the lock detection switch 40 is
in a state of outputting a lock detection signal, the gate lock
on/off valve 33 is in an operating state. As the pilot line 31 is
cut off in this state, no pilot pressure is applied to any of the
hydraulic pilot ports of all the actuator control valves such as
the arm cylinder control valve 27 (the left travel motor control
valve, right travel motor control valve, boom cylinder control
valve, arm cylinder control valve 27, bucket cylinder control
valve, and swing motor control valve), and therefore, all the
actuator control valves assume the initial positions (neutral
positions), respectively. By determining whether or not the lock
detection signal S1 has been applied from the lock detection switch
40, the controller 50 hence functions as a non-operated state
detection means for detecting a non-operated state in which all the
actuator control valves assume the initial positions,
respectively.
[0045] The controller 50 are set to control the boosting control
valve 51 and regulator 52 by outputting the control signals Cp,Cf.
The controller 50 and boosting control valve 51 make up a control
means for controlling the forced regeneration means which is made
up from the regulator 52 and arm cylinder control valve 27.
[0046] The controller 50 is set to determine, based on the boom
angle detection signal Sbm from the boom angle sensor 43, the arm
angle detection signal Sa from the arm angle sensor 41 and the
bucket angle detection signal Sbt from the bucket angle sensor 42,
whether or not the working equipment 7 is in a proper attitude. The
proper attitude is a state in which as illustrated in FIG. 1, the
bucket 10 is folded and carried over the arm 9, the arm 9 is folded
and carried under the boom 8, and the boom 8 has descended with the
end of the arm 9 (the link mechanism 13c) being in contact with a
reference ground level G.
[0047] The controller 50 is set to operate according to steps S1 to
S6 illustrated in FIG. 2-2. The controller 50 is actuated in
association with a stat-up of the engine 23. When the forced
regeneration command signal So is inputted from the forced
regeneration switch 53 after the start-up (YES in step 51), the
controller 50 determines whether or not the input of the lock
detection signal S1 from the lock detection switch 40 is
continuing, namely, whether or not the gate lock lever 32 is in a
locked state (step S2). In parallel with this determination, the
controller 50 also determines, based on the boom angle detection
signal Sbm from the boom angle sensor 43, the arm angle detection
signal Sa from the arm angle sensor 41 and the bucket angle
detection signal Sbt from the bucket angle sensor 42, whether or
not the working equipment 7 is in a proper attitude (step S2).
[0048] When the locked state of the gate lock lever 32 and the
proper attitude are both detected by the determinations in step S2
(YES in step S2), the controller 50 makes the forced regeneration
means (the arm cylinder control valve 27 and regulator 52) initiate
forced regeneration (step S3). In other words, control signals
Cp,Cf which correspond to preset control values are outputted to
the boosting control valve 51 and regulator 52, respectively. No
forced regeneration is initiated unless the locked state of the
gate lock lever 32 and the proper attitude have been both detected
(NO in step S2).
[0049] The boosting control valve 51 to which the control signal Cp
has been applied produces a pilot pressure, and this pilot pressure
is applied to the hydraulic pilot port 27a of the arm cylinder
control valve 27. The valve position of the arm cylinder control
valve 27, therefore, changes from the initial position 27c to the
side of the first operating position 27d. As a result, the arm
cylinder 12 extends, and in addition, the delivery pressure of the
main pump 22 rises. On the other hand, the regulator 52 to which
the control signal Cf has been applied increases the delivery flow
rate of the main pump 22.
[0050] While the gate lock lever 32 is in the locked state, the
engine 23 is controlled in an idling state for energy saving and
noise reduction. In association with an increase in the delivery
flow rate of the main pump 22 and a rise in its delivery pressure,
however, the engine 23 is controlled to increase its output. When
the engine output increases, the temperature of exhaust gas rises
so that particulate matter burns with the heat of the exhaust gas,
in other words, forced regeneration is conducted. During the forced
regeneration, the controller 50 performs adjustments of the control
signal Cp based on the delivery pressure detection signal Sp from
the delivery pressure sensor 44 to maintain the delivery pressure
of the main pump 22 at a predetermined pressure needed for the
forced regeneration or higher.
[0051] From the time point of the initiation of the output of the
control signal Cp to the boosting control valve 51, the controller
50 also determines, based on the arm angle detection signal Sa from
the arm angle sensor 41, whether or not the arm cylinder 12 is in a
stroke-end state on the extended side. Namely, the controller 50
functions as a stroke-end state detection means for detecting that
the arm cylinder 12 is in the stroke-end state on the side where
the free end of the arm 9 is brought closer to the boom 8, that is,
on the extended side. Based on the results of the determination,
the controller 50 applies the control signal Cp to the arm cylinder
control valve 27 such that the stroke-end state of the arm cylinder
12 is maintained.
[0052] The controller 50 counts an elapsed time from the time point
of the initiation of the output of the control signals Cp,Cf in
step S3, and continues the output of the control signals Cp,Cf
until elapse of a predetermined time as long as the detection of
the locked state of the gate lock lever 32 continues. When the
continuous output time of the control signals Cp,Cf has passed the
predetermined time (YES in step S4), the output of these control
signals Cp,Cf is stopped to end the forced regeneration (step S5).
It is to be noted that the predetermined time is set as a time
sufficient to remove particulate matter from the filter of the
exhaust gas purification device 25.
[0053] When the locked state of the gate lock lever 32 has become
no longer detected before the elapse of the predetermined time (NO
in step S4), on the other hand, the controller 50 stops the output
of the control signals Cp,Cf at this time point, and stops the
forced regeneration (step S6).
[0054] According to the hydraulic drive system 20 of the first
embodiment, the following advantageous effects can be brought
about.
[0055] With the hydraulic drive system 20, the operator of the
hydraulic excavator 1 can make the forced regeneration means (the
arm cylinder control valve 27 and regulator 52) initiate forced
regeneration by operating the forced regeneration switch 53 after
bringing the valve positions of all the actuator control valves
such as the arm cylinder control valve 27 into the states of
initial positions, that is, into states, where the hydraulic
excavator 1 is inoperative, by bringing the gate lock lever 32 into
the locked state. As a consequence, the operator can take time
either before initiation of work or after completion of work by the
hydraulic excavator 1 or periodically to purposefully conduct
forced regeneration continuously for a sufficient time. The
hydraulic drive system 20 can, therefore, contribute to the
prevention of a reduction in engine output during operation of the
hydraulic excavator 1, which would otherwise be caused by leaving
localized clogging of the filter uncleaned in the exhaust gas
purification device 25.
[0056] In the hydraulic drive system 20, the arm 9 and boom 8 take
an attitude as a whole during forced regeneration that they are
folded back toward the revolving upperstructure 4 of the hydraulic
excavator 1. As a consequence, the space occupied by the hydraulic
excavator 1 in horizontal direction during the forced regeneration
can be maintained small. Further, as the motion of the arm 9 upon
forced regeneration, the arm 9 is actuated such that its free end
comes closer to the boom 8. Compared with an actuation that moves
the free end of the arm 9 away from the boom 8, the potential
problem that the working equipment 7 may come into contact with an
object around the working equipment 7 can be made hardly occur
accordingly.
[0057] In the hydraulic drive system 20, the stroke-end sate of the
arm cylinder 12 is detected based on the angle of the arm 9
relative to the boom 8, in other words, the attitude of the arm 9
relative to the boom 8. As the hydraulic excavator 1, there is one
having an arm angle sensor 41 arranged irrelevant to forced
regeneration. Using this arm angle sensor, the hydraulic drive
system 20 can detect the stroke-end state of the arm cylinder.
[0058] It is to be noted that, although the above-described
hydraulic drive system 20 according to the first embodiment is
adopted in the backhoe shovel, the present invention is not limited
to one adopted in such a backhoe shovel but may be adopted in a
loading shovel. In a backhoe shovel, however, the stroke end on the
extended side of an arm cylinder corresponds to the state of the
arm cylinder that the free end of the arm is brought closest to the
boom. In a loading shovel, on the other hand, the stroke end on the
contracted side of the arm cylinder corresponds to the state of the
arm cylinder that the free end of the arm is brought closest to the
boom. It is, therefore, necessary to actuate the cylinder control
valve to a side, where the arm cylinder is contracted, when the
actuation of the arm upon force regeneration is set as an actuation
that brings the free end of the arm closer to the boom.
[0059] In the hydraulic drive system 20, the arm cylinder control
valve 27 is used as a specific actuator control valve. However, the
specific control valve in the present invention may be the bucket
cylinder control valve. According to this construction, a part of
the working equipment, said part being to be actuated upon forced
regeneration, is the bucket or an attachment. Compared with the
boom and arm, a change in the attitude of the working machine as a
result of the actuation of such a part is limited smaller. Namely,
the forced regeneration can be conducted in a space smaller than
that required for an actuation of the boom or arm out of the
working equipment. As a hydraulic excavator, there is one provided
with an angle sensor arranged irrelevant to forced regeneration at
a pin joint, which pivotally connects the arm and bucket with each
other, or at a link mechanism interposed between the arm and the
bucket. When the bucket cylinder control valve is the specific
control valve, the stroke-end state of the bucket cylinder can be
detected by using the angle sensor.
[0060] The hydraulic drive system 20 has been described above by
citing as an illustrative proper attitude the state that as
illustrated in FIG. 1, the bucket 10 is folded and carried above
the arm 9, the arm 9 is folded and carried under the boom 8, and
the boom 8 has descended with the free end of the arm 9 (the link
mechanism 13c) being in contact with the referenced ground level G.
The proper attitude may, however, be other than the illustrated
state. The proper attitude may be a state that only the arm is
folded and carried under the boom, a state that only the bucket is
folded and carried above the arm, or a state that only the arm and
bucket are both folded under the boom. In other words, it is
possible to adopt as a proper attitude insofar as at least one of
the boom, arm and bucket is in such a state that it has been driven
to a movable limit angle.
Second Embodiment
[0061] With reference to FIGS. 3-1 and 3-2, a description will be
made about the second embodiment of the present invention. FIG. 3-1
is a hydraulic circuit diagram showing in a simplified form a
hydraulic drive system according to the second embodiment of the
present invention. FIG. 3-2 is a flow chart illustrating a flow of
processing to be performed at a controller depicted in FIG. 3-1.
Among elements and signals illustrated in FIG. 3-1, like elements
and signals to the corresponding ones illustrated in FIG. 2-1 are
designated using like reference signs.
[0062] In the hydraulic drive system 60 according to the second
embodiment, the actuator control valves such as the arm cylinder
control valve 27 are constructed such that they can be electrically
controlled. Taking the arm cylinder control valve 27 as an example,
a description will be made. The hydraulic pilot port 27a of the arm
cylinder control valve 27 is provided with a proportional solenoid
valve 62 as an accessory. The hydraulic pilot port 27b of the arm
cylinder control valve 27 is provided with a proportional solenoid
valve 63 as an accessory. The proportional solenoid valve 62
produces a pilot pressure, which is to be applied to the hydraulic
pilot port 27a, by using the delivery pressure of the pilot pump 28
as a primary pressure. The proportional solenoid valve 63 produces
a pilot pressure, which is to be applied to the hydraulic pilot
port 27b, by using the delivery pressure of the pilot pump 28 as a
primary pressure. A control signal Ce to be applied to a solenoid
of the proportional solenoid valve 62 and a control signal Cc to be
applied to a solenoid of the proportional solenoid valve 63 are
both outputted from a controller 64.
[0063] The controller 64 is a unit, which has CPU, ROM, RAM and the
like and is operated in accordance with a computer program.
Inputted to the controller 64 are the boom angle detection signal
Sbm outputted from the boom angle sensor 43, the arm angle
detection signal Sa outputted from the arm angle sensor 41, the
bucket angle detection signal Sbt outputted from the bucket angle
sensor 42, the delivery pressure detection signal Sp outputted from
the delivery pressure sensor 44, and the forced regeneration
command signal So outputted from the forced regeneration switch
53.
[0064] To the controller 64, an actuation command signal Ea
(electrical signal) which corresponds to a command value for the
actuation of the arm cylinder 12 is inputted from an arm control
device 29. The arm control device 29 has a lever-operated variable
resistor, and outputs the control direction and control quantity of
the control lever by converting them into the actuation command
signal as an electrical signal. The controller 64 is set to compute
control values for the proportional solenoid valves 62,63 based on
the actuation command signal and to output control signals Ce,Cc
corresponding to the control values. The proportional solenoid
valves 62, 63 are spring-return control valves. In the proportional
solenoid valve 62, an initial position 62a is a valve position in
which a passage is formed to bring the hydraulic pilot port 27a
into communication with the hydraulic oil reservoir 21, while an
operating position 62b is a valve position in which a passage is
formed to bring the hydraulic pilot port 27a into communication
with the pilot pump 28. A pilot pressure to be applied to the
hydraulic pilot port 27a changes steplessly depending on changes in
the valve position of the proportional solenoid valve 62, and
becomes higher as the valve position comes closer to the operating
position 62b. The proportional solenoid valve 63 is also
constructed like the proportional solenoid valve 62.
[0065] The actuator control valves other than the arm cylinder
control valve 27, that is, the boom cylinder control valve, bucket
cylinder control valve, left travel motor control valve, right
travel motor control valve and swing motor control valve are also
provided with proportional solenoid valves as accessories, which
are similar to the proportional solenoid valves 62,63 for the arm
cylinder control valve 27. Like the arm control device 29 for the
arm cylinder control valve 27, the boom cylinder control valve,
bucket cylinder control valve, left travel motor control valve,
right travel motor control valve and swing motor control valve are
also provided with control devices, respectively. By these control
devices, actuation command signals (electrical signals)
corresponding to command values for the actuation of the boom
cylinder, arm cylinder, left travel motor, right travel motor and
swing motor are inputted to the controller 64. Based on actuation
command signals from the respective control devices other than the
arm control device 29, the controller 64 computes, in a similar
manner as for the actuation command signal Ea from the arm control
device, control values for the proportional solenoid valves
arranged as accessories for the actuator control valves
corresponding to the actuation command signals, and outputs control
signals corresponding to the control values.
[0066] The controller 64 is set to determine whether or not an
actuation command signal has not been outputted from any of all the
control devices such as the arm control device 61. In a state that
no actuation command signal has been outputted from any of all the
control devices, the controller 64 does not give a control signal
to any of the proportional solenoid valves arranged as accessories
for all the actuator control valves (the left travel motor control
valve, right travel motor control valve, boom cylinder control
valve, arm cylinder control valve 27, bucket cylinder control
valve, swivel motor control valve). Accordingly, no pilot pressure
is applied to any of the hydraulic pilot ports of all the actuator
control valves such as the arm cylinder control valve 27, whereby
all the actuator control valves assume the initial positions
(neutral positions). Namely, the controller 64 functions as a
non-operated state detection means for detecting a non-operated
state, in which all the actuator control valves assume the initial
positions, by determining whether or not the hydraulic drive system
is in a state in which no actuation command signal has been
outputted from any of all the control devices such as the arm
control device 61.
[0067] Similar to the controller 50 in the first embodiment, the
controller 64 is also set to determine, based on the boom angle
detection signal Sbm from the boom angle sensor 43, the arm angle
detection signal Sa from the arm angle sensor 41 and the bucket
angle detection signal Sbt from the bucket angle sensor 42, whether
or not the working equipment 7 is in a proper attitude.
[0068] In the second embodiment, the regulator 52 and arm cylinder
control valve 27 make up a forced regeneration means as in the
first embodiment. Different from the first embodiment, however, a
control means for this forced regeneration means is made up from
the controller 64 and proportional solenoid valve 62.
[0069] The controller 64 is set to operate according to steps S11
to S16 illustrated in FIG. 3-2. The controller 64 is actuated in
association with a stat-up of the engine 23. When the forced
regeneration command signal So is inputted from the forced
regeneration switch 53 after the start-up (YES in step S11), the
controller 64 determines whether or not no actuation command signal
has been inputted from any of all the control devices such as the
arm control device 61, namely, whether or not there is no actuation
command (step S12). In parallel with this determination, the
controller 64 also determines, based on the boom angle detection
signal Sbm from the boom angle sensor 43, the arm angle detection
signal Sa from the arm angle sensor 41 and the bucket angle
detection signal Sbt from the bucket angle sensor 42, whether or
not the working equipment 7 is in a proper attitude (step S12).
[0070] When the state of no actuation command from any control
device and the proper attitude are both detected by the
determinations in step S12 (YES in step S12), the controller 64
makes the forced regeneration means (the arm cylinder control valve
27 and regulator 52) initiate forced regeneration (step S13). In
other words, control signals Ce,Cf which correspond to preset
control values are outputted to the proportional solenoid valve 62
and regulator 52, respectively. No forced regeneration is initiated
unless the state of no actuation command from any control device
and the proper attitude have been both detected (NO in step
S2).
[0071] The proportional solenoid valve 62 to which the control
signal Ce has been applied produces a pilot pressure, and this
pilot pressure is applied to the hydraulic pilot port 27a of the
arm cylinder control valve 27. The valve position of the arm
cylinder control valve 27, therefore, changes from the initial
position 27c to the side of the first operating position 27d. As a
result, the arm cylinder 12 extends, and in addition, the delivery
pressure of the main pump 22 rises. On the other hand, the
regulator 52 to which the control signal Cf has been applied
increases the delivery flow rate of the main pump 22.
[0072] While all the actuators are in non-operated states, the
engine 23 is controlled in an idling state for energy saving and
noise reduction. In association with an increase in the delivery
flow rate of the main pump 22 and a rise in its delivery pressure,
however, the engine 23 is controlled to increase its output. When
the engine output increases, the temperature of exhaust gas rises
so that particulate matter burns with the heat of the exhaust gas,
in other words, forced regeneration is conducted. During the forced
regeneration, the controller 64 performs adjustments of the control
signal Ce based on the delivery pressure detection signal Sp from
the delivery pressure sensor 44 to maintain the delivery pressure
of the main pump 22 at a predetermined pressure needed for the
forced regeneration or higher.
[0073] From the time point of the initiation of the output of the
control signal Ce to the proportional solenoid valve 62 in step
S13, the controller 64 also determines, based on the arm angle
detection signal Sa from the arm angle sensor 41, whether or not
the arm cylinder 12 is in the stroke-end state on the extended
side. Namely, the controller 64 functions as a stroke-end state
detection means for detecting that the arm cylinder 12 is in the
stroke-end state on the side where the free end of the arm 9 is
brought closer to the boom 8, that is, on the extended side. Based
on the results of the determination, the controller 64 applies the
control signal Ce to the proportional solenoid valve 62 such that
the stroke-end state of the arm cylinder 12 is maintained.
[0074] The controller 64 counts an elapsed time from the time point
of the initiation of the output of the control signals Ce,Cf, and
continues the output of the control signals Ce,Cf until elapse of a
predetermined time as long as the detection of the state of no
actuation command from any control device continues. When the
continuous output time of the control signals Ce,Cf has passed the
predetermined time (YES in step S14), the output of these control
signals Ce,Cf is stopped to end the forced regeneration (step S15).
It is to be noted that the predetermined time is set as a time
sufficient to remove particulate matter from the filter of the
exhaust gas purification device 25.
[0075] When the state of no actuation command from any control
device has become no longer detected before the elapse of the
predetermined time (NO in step S14), on the other hand, the
controller 64 stops the output of the control signals Ce,Cf at this
time point, and stops the forced regeneration (step S16).
[0076] According to the hydraulic drive system 60 of the second
embodiment, the following advantageous effects can be brought
about.
[0077] With the hydraulic drive system 60, the operator of the
hydraulic excavator 1 can make the forced regeneration means (the
arm cylinder control valve 27 and regulator 52) initiate forced
regeneration by operating the forced regeneration switch 53 after
bringing the valve positions of all the actuator control valves
such as the arm cylinder control valve 27 into the states of
initial positions, that is, into states, where the hydraulic
excavator 1 is inoperative, by stopping operation of all the
control devices such as the arm control device 29. As a
consequence, the operator can take time either before initiation of
work or after completion of work by the hydraulic excavator 1 or
periodically to purposefully conduct forced regeneration
continuously for a sufficient time. The hydraulic drive system 60
can, therefore, contribute to the prevention of a reduction in
engine output during operation of the hydraulic excavator 1, which
would otherwise be caused by leaving localized clogging of the
filter uncleaned in the exhaust gas purification device 25.
[0078] In the hydraulic drive system 60, the arm 9 and boom 8 take,
as in the hydraulic drive system 20 according to the first
embodiment, an attitude as a whole during forced regeneration that
they are folded back toward the revolving upperstructure 4 of the
hydraulic excavator 1. As a consequence, the space occupied by the
hydraulic excavator 1 in horizontal direction during the forced
regeneration can be maintained small. Further, as the motion of the
arm 9 upon forced regeneration, the arm 9 is actuated such that its
free end comes closer to the boom 8. Compared with an actuation
that moves the free end of the arm 9 away from the boom 8, the
potential problem that the working equipment 7 may come into
contact with an object around the working equipment 7 can be made
hardly occur accordingly.
[0079] In the hydraulic drive system 60, the stroke-end sate of the
arm cylinder 12 is also detected, as in the hydraulic drive system
20 according to the first embodiment, based on the angle of the arm
9 relative to the boom 8, in other words, the attitude of the arm 9
relative to the boom 8. As the hydraulic excavator 1, there is one
having an arm angle sensor 41 arranged irrelevant to forced
regeneration. Using this arm angle sensor, the hydraulic drive
system 20 can detect the stroke-end state of the arm cylinder.
[0080] In the above-described hydraulic drive system 60 according
to the second embodiment, the non-operated state detection means
relies upon determining whether or not no actuation command signal
has been outputted to the controller 64 from any of all the control
devices. However, the non-operated state detection mean is not
limited to such a means, but can be a similar non-operated state
detection means as in the hydraulic drive system according to the
first embodiment, specifically one capable of detecting a
non-operated state by determining whether or not the gate lock
lever 32 is in the locked state based on whether or not a lock
detection signal has been outputted from the lock detection switch
40.
[0081] Similar to the above-described hydraulic drive system 20
according to the first embodiment, the hydraulic drive system 60 is
also adopted in the backhoe shovel. However, the present invention
is not limited to one adopted in such a backhoe shovel but may be
adopted in a loading shovel.
[0082] In the hydraulic drive system 60, the arm cylinder control
valve 27 is also used as a specific actuator control valve as in
the hydraulic drive system 20 according to the first embodiment.
However, the specific control valve in the present invention may be
the bucket cylinder control valve.
Legend
[0083] 1 Hydraulic excavator [0084] Travel base [0085] 3 Crawler
track [0086] 4 Revolving upperstructure [0087] 5 Operator's cab
[0088] 6 Engine compartment [0089] 7 Working equipment [0090] 8
Boom [0091] 9 Arm [0092] 10 Bucket [0093] 11 Boom cylinder [0094]
11a Cylinder tube [0095] 11b Rod [0096] 12 Arm cylinder [0097] 12a
Cylinder tube [0098] 12a1 Bottom chamber [0099] 12a2 Rod chamber
[0100] 12b Rod [0101] 13 Bucket cylinder [0102] 13a Cylinder tube
[0103] 13b Rod [0104] 13c Link mechanism [0105] 20 Hydraulic drive
system [0106] 21 Hydraulic oil reservoir [0107] 22 Main pump [0108]
23 Engine [0109] 24 Exhaust gas pipe [0110] 25 Exhaust gas
purification device [0111] 26 Outlet pipe [0112] 27 Arm cylinder
control valve [0113] 27a, 27b Hydraulic pilot ports [0114] 27c
Initial position [0115] 27d First operating position [0116] 27e
Second operating position [0117] 28 Pilot pump [0118] 29 Arm
control device [0119] 30 Main line [0120] 31 Pilot line [0121] 32
Gate lock lever [0122] 33 Gate lock on/off valve [0123] 40 Lock
detection switch [0124] 41 Arm angle sensor [0125] 42 Bucket angle
sensor [0126] 43 Boom angle sensor [0127] 44 Delivery pressure
sensor [0128] 50 Controller [0129] 51 Boosting control valve [0130]
51a Initial position [0131] 51b Operating position [0132] 52
Regulator [0133] 53 Forced regeneration switch [0134] 60 Hydraulic
drive system [0135] 62 Arm control device [0136] 62 Proportional
solenoid valve (PSV) [0137] 62a Initial position [0138] 62b
Operating position [0139] 63 Proportional solenoid valve (PSV)
[0140] 64 Controller
* * * * *